The present invention relates to the field of heat exchange, and provides a heat exchanger especially suited for use in a catalytic fuel reformer.
In fuel reforming reactions, hydrogen is produced from methane, or from other hydrocarbons, especially for the purpose of operating a fuel cell. In a fuel cell, hydrogen is consumed in the process of producing electric power, and therefore a continuous supply of hydrogen is required. These fuel reforming reactions may be either endothermic, such as in the case of steam reforming, or exothermic, such as in the case of catalytic partial oxidation. All involve the need to add heat to, or to remove heat from, the reforming reaction. Thus, such reactions require a method of heat exchange.
In copending patent application Ser. No. 10/211,083, filed Aug. 2, 2002, and Ser. No. 10/347,130, filed Jan. 17, 2003, the disclosures of which are incorporated by reference herein, there are described steam reformers in which the heat required for the steam reforming is provided by catalytic combustion of a fuel. The steam reforming reaction occurs in channels that are in heat exchange relationship with combustion channels. In the above-cited applications, a conventional heat exchanger provides a structure that defines the necessary combustion and reforming channels.
The conventional heat exchanger used in the above-cited applications is not a perfect choice for use in catalytic steam reforming or for other catalytic reforming reactions. The conventional heat exchanger is made of a plurality of rigid and relatively heavy plates which are carefully welded together to prevent leakage of gas. This construction substantially increases the cost of the device. Moreover, it is difficult to apply a catalyst coating to all of the interior surfaces of the finished heat exchanger.
The present invention solves the above-described problems by providing a heat exchanger that can be built from a piece of metal foil. The present heat exchanger avoids most of the welding required in conventional heat exchangers, and the use of thin foil promotes efficient heat transfer between adjacent channels. Also, it is easy to apply a catalyst coating to all of the interior surfaces of the present heat exchanger, due to its unique construction.